Looped traffic accessory

ABSTRACT

A flexible track for toy vehicles has one end connected to a bracket on a C clamp, the clamp being engaged with an elevated support so the track droops to the floor below. Accessory means in the form of starting gates, loops, ski jumps, banked curves, finish gates, and track mergers may be connected to the track to interact with toy vehicles.

llnite Slates ate rigliam et al.

LOOPED TRAFFIC ACCESSORY Inventors: Emerson W. Brigham, Hermosa Beach; Harvey W. La Branche, Palos Verdes Peninsula; Alan W. B.

Nash, Torrance; Howard F. New-- man, Los Angeles; Thomas E. See, Huntington Beach; Marjorie Ann M. Smith, Gardena; Arthur S. Woodward, Sylmar, all of Calif.

Assignee: Mattel, llnc., Hawthorne, Calif.

Filed: Aug. 113, 1970 Appl. No.: 63,589

Related US. Application Data Division of Ser. No. 785,135, Dec. 19, 1968, abancloned.

U.S. Cl. ..238/l0 1E, 104/55 Int. Cl. ..A63h 19/36 Field of Search 104/55, 60;

238/10 E, 10 F; 46/43, 1 K

[4 1 May 29, 1973 [56] References Cited UNITED STATES PATENTS 3,411,783 11/1968 Montagna ..104/55 3,480,210 11/1966 Perrinjaquet 1,431,398 10/1922 Hetener 1,725,536 8/1929 Marx ..l04/55 OTHER PUBLICATIONS Mattel Toy Catalog, Received March 14, 1968, Hot Wheels, pages 4-10.

Primary Examiner-Gerald M. Forlenza Assistant ExaminerRichard A. Bertsch AttorneySeymour A. Scholnick [57] ABSTRACT A flexible track for toy vehicles has one end connected to a bracket on a C clamp, the clamp being engaged with an elevated support so the track droops to the floor below. Accessory means in the form of starting gates, loops, ski jumps, banked curves, finish gates, and track mergers may be connected to the track to interact with toy vehicles.

2 Claims, 31 Drawing Figures tented May 29, 1973 3,735,923

9 Sheets-Sheet 2 Pmmm 9 Sheets-Sheet 4 Patented May 29, 1973 3,735,923

9 Sheets-Sheet 6 Fatented May 29, 1973 9 Sheets-Sheet 7 Patented May 29, 1973 9 Sheets-Sheet 9 LOOPED TRAFFIC ACCESSORY CROSS REFERENCE TO RELATED APPLICATION This application is a Division of application Ser. No. 785,135, filed Dec. 19, 1968, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to small car action toys.

2. Description of the Prior Art Track systems for small toy cars are usually designed to be assembled on a living room floor for use with powered toy vehicles. If unpowered toy vehicles are to be used, small inclined frames may be included to form a small hill down which the vehicles can roll to gain speed. However, cost and packaging restrictions limit such frames to small hills, which results in low vehicle speed and inability to traverse long track layouts or properly move over accessories that require high vehicle speeds. Prior art track systems also do not readily lend themselves to arrangements for using two tracks together to provide racing games and stunt action sets where vehicles from the two tracks interact.

SUMMARY OF THE INVENTION One object of the present invention is to provide an economical track layout which enables unpowered toy vehicles to gain high speed.

Another object is to provide novel and entertaining accessory means for a toy track system.

In accordance with the present invention, a small car action toy is provided which includes track means forming a path for a toy vehicle. The track means is adapted to be connected to an elevated support, so one end can be raised to a substantial height. The track means is flexible to enable it to droop from the elevated support to the floor below so that at least some of the following track portions are supported by the floor.

Accessory means are provided which may be connected to the track means for changing the action of vehicles along the path of travel. The accessory means include a starting gate, a finish gate, a loop, a ski jump, a banked curve, and a merger (for merging two tracks into a single track). The track means includes individual track sections of short length for facilitating packaging, and connector means for connecting the track sections together.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawmgs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a small car action toy constructed in accordance with the invention;

FIG. 2 is a perspective view of connector means and starting gate accessory means of the action toy of FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a partial sectional view taken on the line 55 of FIG. 3;

FIG. 6 is a perspective view of loop-forming accessory means of the action toy of FIG. 1;

FIG. 7 is a partial plan view of a portion of the accessory means shown in FIG. 6;

FIG. 8 is a sectional view taken on line 8-8 of FIG.

FIG. 9 is a sectional view taken on line 9-9 of FIG.

FIG. 10 is a sectional view taken on line l010 of FIG. 7;

FIG. 11 is a plan view of banked curve accessory means of the action toy of FIG. 1;

FIG. 12 is a sectional view taken on line 1212 of FIG. 11;

FIG. 13 is a sectional view taken on line 13-13 of FIG. 11;

FIG. 14 is a partial perspective view of the accessory means of FIG. 11;

FIGS. 15 and 16 are exploded, partial perspective views illustrating the connection of the ends of the accessory means of FIG. 11 to the track means of FIG. 1;

FIG. 17 is a perspective view of a trestle of the action toy of FIG. 1, shown with a section of track to which it can be connected;

FIG. 18 is a partial elevation view demonstrating how a trestle of the type shown in FIG. 17 may be placed on top of a second trestle;

FIG. 19 is a perspective view of ski jump accessory means of the action toy of FIG. 1;

FIG. 20 is a sectional view taken on line 2020 of FIG. 19;

FIG. 21 is a partial sectional view taken on line 2I2l of FIG. 20;

FIG. 22 is an elevation view of a second banked curve of the action toy of FIG. 1;

FIG. 23 is a sectional view taken on line 2323 of FIG. 22;

FIG. 24 is a sectional view taken on line 24-24 of FIG. 22;

FIG. 25 is a partial plan view of the accessory means of FIG. 22;

FIG. 26 is a perspective view of finish gate accessory means of the action toy of FIG. 1;

FIG. 27 is a sectional view taken on line 27-27 of FIG. 26;

FIG. 28 is a sectional view taken on line 28-28 of FIG. 26;

FIG. 29 is a sectional view taken on line 2929 of FIG. 26;

FIG. 30 is a perspective view of track merger accessory means of the action toy of FIG. 1; and

FIG. 31 is a sectional view taken on line 31-31 of FIG. 30.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a small car action toy constructed in accordance with the invention, which is generally designated at 10. The toy includes track means 12 forming a path for toy vehicles, such as vehicles 14 and 16. The track 12 includes a first end 18 adapted to be attached to an elevated support 20, such as a table top, by connector means 22. The track has sufficient flexibility that it droops from support 20 to the floor, so that at least one portion of the track means is supported by the floor. Thus, toy vehicles initially move down a long steep incline so that they have sufficient speed to properly traverse the track course.

The action toy includes accessory means which may be connected in series with the track to interact with the vehicles in a novel manner. FIG. 1 illustrates seven of such accessory means including a starting gate 36, a loop 24, a 90 curve 26, a ski jump 28, a 180 curve 30, a finish gate 32, and a track merger 34. Duplicate accessory means including a second track 12A, second loop 24A, second 90 curve 26A, second ski jump 28A, and second 180 curve 30A can also be provided for a second of the cars. By starting the cars 14 and 16 together at the starting gate 36, they can be made to race over similar courses to the finish gate 32, and then through the merger 34 to a common track 284.

FIGS. 2 through shows details of the starting gate accessory means 36, which may be used to simultaneously start the cars 14, 16 (shown by arrows in FIG. 2) for a race. The starting gate includes a frame or housing 38 having a bottom wall 40, a top wall 42, a rear wall 44, a front wall 46 and a pair of side walls 48, 50. The top wall 40 serves as a starting surface to hold the cars 14, 16 in a laterally spaced relationship so they can move over different tracks. The side walls 48, 50 have comparatively narrow front portions 52 and wide rear portions 54, causing the top wall 42 to slope downwardly from its rear end 58 to its front end 56 so that the cars 14, 16 will be accelerated by gravity when they are permitted to roll down top wall 42.

Cars 14, 16 are retained in position on top wall 42 by stop members 60, 62, respectively, that abut the front bumpers of the cars. The stop members 60, 62 are carried by laterally-extending flanges 64, 66, respectively. The flanges 64, 66 are supported on an actuator 65 that is pivotally connected to top wall 42 by a living hinge at 67. A living hinge is a reduced-section in an integral member of flexible material such as polypropylene.

Actuator 65, which is designed for manual operation, i.e. by a child pressing down on it, is biased to the position shown in FIGS. 1 through 4 by a rod-like cantilever spring 70. This spring 70 has its free end 72 engaged in an inverted, V-shaped slot 74 provided in a depending plate 76 carried by actuator 65. The fixed end 78 of the spring is affixed to a shelf 80 provided on bottom wall 40, by a retaining clip 82. When the actuator 65 is depressed by a child, the stop members move down simultaneously through apertures 81, 83 in the top wall, thereby simultaneously releasing the vehicles.

The starting gate accessory means 36 also includes a pair of integral connectors 84, 86 which extend forwardly and downwardly from front wall 46, at the downpath end of the frame, for receiving the end 18 of track means 12 and the end 18A of a parallel track means 12A, respectively, which droop towards the floor. Connectors 84, 86 are adapted to engage channels 87 and 88 provided in tracks 12, 12A, respectively. Connectors 84, 86 are retained in position within their associated channels 87, 88 by protruberances 90, 92. The protuberances 90 and 92 extend from opposite facesof the connectors to enable tight engagement with the connecting track sections.

The starting gate 36 may be connected to the table or other elevated support by the connector means 22. The connector means is in the form of a C clamp with an anvil 94 and a screw 96. The anvil is placed over an edge of the table, and the screw 96 is then tightened to hold it in place. The connector means or clamp 22 has a bracket or land 98 which is designed to hold a section of track 12 by engaging the walls of the channel 87 therein. However, it also can engage a channel 100 provided in bottom wall 40 of the starting gate 36. In addition to the land 98, the clamp is provided with a pair of lands 102, 104 on the long leg 106 of the anvil. The pair of lands 102 and 104 are employed when the clamp engages a vertically extending board of table top means, instead of a horizontal table top, since engagement with a vertical board results in only the lands 102 and 104 being almost horizontal. The two lands 102 and 104 enable two parallel tracks to be connected to the clamp when this is desired. In order to attach the clamp to a table, the screw 96, which threadably engages a first short leg 108 on the clamp anvil, is turned to advance it toward a second short leg 110, to hold the table 20 between the screw and the second short leg. The second short leg 1 10 has cutaway portions 111 and 113 that can receive edge molding and the like which may be present at the table top means. The portion 111 is designed to receive strips of decorative trim, while the portion 113 is designed to receive piping that is generally present at the edges of sofa cushions, matresses, and other upholstered pieces which serve as elevated table top means to be clamped onto.

FIGS. 6-10 illustrate the loop accessory means or loops 24, 24A. Each includes a usually straight track section 116 which is held in the shape of a loop by a loop-forming frame or jig 118. The jig of each loop such as loop 24 may be conveniently molded from a suitable plastic material in two identical halves 120 and 121. Each half 120, 121 includes a base 122 carrying an integrally-formed arcuate track section 124. The arcuate track section 124 has a first end merging into a connector 128 for connection to the main track 12 (or track 12A, as the case may be). The arcuate track section also has a second elevated end 130 merging into a long curved connector 132 for joining to an end of track section 116, by engaging channels 87 of track section 116. Stand portions 131,133 support the jig halves on the floor. The identical halves 120 and 121 may be connected together by brackets 134, 135 formed on the jig halves during the molding operation. Each bracket 134, 135 includes a keyhole slot 136 at one end and a protuberance 138 at the other end. With this arrangement, identical jig halves may be connected by reversing them and engaging protuberances 138 on one jig half into the keyhole slot 136 on the other jig half.

The end 126 of the jig half receives vehicles moving substantially parallel to the ground, while the arcuate track sections 124 of the jig halves establish a one-turn helix for the vehicles. Finally, the vehicles are discharged at the end 126 of the other jig half 121 in a direction substantially parallel to the ground, and moving in the same direction as they were received. The vehicles must have an appreciable speed in order to pass around the loop. The speed attained by passing down a long incline from a table top generally is sufficient to enable passage around a small loop, in spite of frictioncaused decreases in speed prior to reaching the loop.

FIGS. 11-16 show details of the 90 curve accessory 26, which is shown supported above the ground by a bridge support or trestle 140. As shown in FIG. 11, the curve comprises a frame 142 which supports a curved and banked track portion 144 for connection in series with the main track 12. A connector 146, 148 is formed at each end of the track portion, for engagement with the channel on the underside of an adjoining track section. The frame can be laid on the floor, or can be supported by the trestle 140 by engagement of the trestle with a bracket 150 on the frame. As shown in FIG. 13, the frame includes a support wall 151 which can support the outer edge of the curved track when the frame rests on the floor.

The banking of the curve varies from a preliminary level such as at each end 152 and 154, as shown in FIG. 12, to a high level such as 55 at the center 156, as shown in FIG. 13. The substantial preliminary banking away from a horizontal plane at each end, twists the adjoining track sections into a gradually increasing banking angle. As a result, the rotation of the vehicles about their longitudinal axes while entering and leaving the banked track area occurs more gradually. A more rapid angular acceleration of the vehicles about their longitudinal axes would tend to make them unstable. While the same low angular acceleration could be achieved by using a larger curve, this would add to the cost of the accessory. It if often desirable to support the curve accessory above the ground, as on the trestle 140, to hold adjacent portions of track 12 above the ground where they can easily be twisted into the initial banking angle.

FIGS. 15 and 16 illustrate the manner of connection of the curve accessory 26 with a track 12. If it is assumed that the vehicles will move in the direction of arrows 158, then the vehicles will leave the curve at the end having the connector 148. It is desirable to bend over slightly the side walls 13 of the track to prevent a vehicle wheel from hitting a protruding side wall. Similarly, the sides of the curved track portion 144 can be bent outwardly slightly at the end 152 where the vehicles enter the curve.

FIG. 17 shows details of the trestle 140, which is designed to support a simple track section, as well as some of the accessories such as the curve 26 described above. The trestle includes a bridge-like frame 160 which has a flat-topped bracket or land 162 on an upper beam 164. The land has eight sides for facilitating engagement with a track member, such as an accessory or a simple track 12 which has walls forming continuous channels 87. The large sides 166 of the land are a distance G apart, while the small sides 168 are spaced a larger distance II apart.

In order to attach the trestle 140 to a track 12, the track is placed on the trestle with the track channels 87 formed by channel member 89 that extend toward each other, oriented parallel to the long sides 166. Then the trestle is turned 45 so that the short sides 168 enter the channels 87. In comparing the trestle land with the track 12, it may be noted that the spacing G of the long sides of the trestle land is slightly less than the spacing G of the closest portions of the channel members 89. Also, the spacing H of the short trestle sides is only slightly less than the width H between the bottom of the track channels 87 into which the short sides fit. This construction allows firm engagement of the trestle with the track member by a simple twist. The trestle does not have to be started at one end ofa track section and slid all the way down to its final place.

The trestle 140 is designed for attachment to another trestle on top of it, for a two or greater level interchange. The legs 170 and 172 of the trestle frame 160 have undercut keyways 174 in them, while keys 176 are formed on each side of the trestle beam 164. FIG. 18 illustrates the manner in which a key 176 of one trestle fits into the keyway of another trestle. The engagement is made by sliding the ends of the keys into the keyways.

FIGS. 19 through 21 illustrate the ski jump accessory 28 which allows a fast-moving vehicle to fly through the air for a small distance. The jump comprises two identical ramp members or jump sections 180 and 182, placed so that there is a gap between them. One jump section 180 is used to direct a vehicle over the gap while the other 182 receives the flying vehicle. The jump section 180 includes a frame 184 which has an inclined track portion 186. High walls 188 extend along each side of the track portion. The walls 188 are curved or flared outward at the upper part 190 of the incline, but at the bottom of the incline they are spaced approximately the same as the side walls of the rest of the track system. The lower part 192 has a connector 194 for reception in the channel 87 of an adjoining track 12, to hold it to the adjoining track.

The frame 184 includes a stand 196 for supporting the upper end 190 of the track portion above the ground. The stand 196 is constructed as a separate unit to facilitate packaging. It is joined to the track portion by keys 198 in the track portion that fit into keyways 200 in the stand. The jump is set up by placing two jump sections at a particular spacing so that the vehicles can fly across when they are traveling at the anticipated speed. The sections should be aligned with each other, although the outward flaring of the sides 188 alows the vehicles to be captured even with considerably misalignment. The side walls 188 are preferably considerably higher than the maximum diameter H of the vehicle wheels of vehicles generallymoved over the jump, and are generally higher than the bodies of the vehicles. This is to facilitate capturing a speedy vehicle that has jumped high.

FIGS. 22 through 25 illustrate a 180 curve accessory means 30. This member is constructed in a manner similar to the curve described above, in that is has end portions 202 and 204 which are banked at an appreciable angle such as 20. The center 206 of the track portion 208 is banked even more, such as an angle of 55. As mentioned above in the case of the 90 curve accessory, the initial banking causes the track sections connected to each end of the curve to be twisted into a gradually increasing banking. This reduces angular acceleration of the vehicle about a longitudinal axis to promote its stability. The curve accessory includes connectors 210 and 212 at each end for connecting to adjoining track sections. A frame 214 supports its track portion either on the ground or on trestles. A pair of brackets 216 and 218 similar to the bracket on the 90 curve, enable attachment to trestles.-

FIGS. 26 through 29 illustrate the finish gate accessory means 32 for use when racing two vehicles, to indicate which vehicle has won. The finish gate includes a frame .220 with a pair of laterally spaced connector lands or brackets 222 and 224 on its bottom member 226. The brackets are designed to be received into the channels 87 and 88 on the under side of the tracks 12 and 12A and to be moved along the length of the track sections to a desired location. Thus, vehicles traveling on the tracks 12, 12A pass through the finish gate and continue moving along the tracks. 4

A flagging member 232 which is pivotally mounted at a shaft 234 on the frame, can fall to either side to indicate which of the two cars has won. The flagging member is operated by a pair of levers 236 and 238 which are pivotally mounted on the top member 240 of the frame.

The levers 236,238 have lower ends 242,244 which are designed to be struck by the vehicles so that they pivot the lever backwards and upwards. Prior to the levers being struck by a vehicle, holding elements 246 and 248 on the levers engage the flagging member to maintain it in an upright position. However, the first lever to be struck releases the flagging member to allow it to fall towards its side of the frame. The lever then falls until it is stopped by one of the stop ledges 250 or 252 on the frame sides 254,256.

The shaft 234, which pivotally supports the flagging member, is engaged with a bearing member 258 at the bottom of a bracket 260 that depends from the top member 240 of the frame. A knob 262 at the end of the shaft 234 retains it in place. The shaft 234 is located below the center of gravity of the flagging member, so that once the flagging member begins to fall to one side, it continues to fall until it hits a stop ledge. However, unless the flagging member is made to start falling to one side, it is uncertain as to which direction it will fall. The levers 236 and 238 are constructed to make sure that the flagging member will fall toward the lever that is first moved back by a vehicle, as will be described below.

As shown in FIG. 28, the levers, such as lever 238, are pivotally joined to a support 262 on the top member 240 by a living hinge 264. The living hinge comprises an area of reduced cross section in a flexible material such as polypropylene. The flexible material out of which the lever is constructed allows it to twist slightly which is important in the operation of the device. As shown in FIG. 29, the holding elements 246 and 248 have edges 266 and 268 that engage opposite sides of the flagging member 232. The width W of the flagging member is greater than the separation of the forward portions of edges 266 and 268 when the levers 236 and 238 are unstressed. Thus, in order to fit between the forward part of the edges 266, 268, the levers 236, 238 must be bent or twisted apart slightly.

Outward movement of the edges 266, 268 that hold the flagging member is accomplished by slight twisting of the levers. When one of the levers, such as lever 236, is pushed back by a first vehicle, the backward movement of its holding element 246 allows the flagging member to fall to the left side, in the direction of arrow 270. The holding element 248 of the other lever 238 helps by thrusting the flagging member in the direction of arrow 270, while the lever 238 untwists. This provides a positive movement of the flagging member to one side. If a second car hits the lever 238 a moment later, it will have no effect because the flagging member has already started to fall to the left. In order to increase the thrust on the flagging member, the edges 266 and 268 are angled so the levers twist even more as one lever is pushed back. The angling also allows the levers to be only slightly stressed until the last moment when a car hits a lever, so that the introduction of permanent set is minimized.

The flagging member 232 is provided with a checkered design simulating the checkered flags generally used at the finish of auto races. A handle 272 is provided to aid in grasping the flagging member during resetting. Resetting for a new race is accomplished by moving the flagging member upright and slightly spreading apart the levers so that the holding elements 246, 248 lie on opposite sides of the flagging member.

FIGS. 30 and 31 illustrate merger accessory means 34 for allowsing vehicles received from two track sections 280 and 282 to travel along a single track section 284. The merger apparatus comprises a track portion 286 having a wide up-path end 288, which is at least as wide as two track sections, with connectors 290 and 292 for connection with the track sections 280 and 282. Side walls 294 and 296 continually narrow the track portion from a position near the up-path end until it is only as wide, at the downpath end 298, as the path ofa single track section. The side walls 294 and 296 are almost parallel at the up-path end, but they quickly curve so they are angled toward each other at a continually increasing angle. At a position 298 they gradually turn the other way, so they are at a continually decreasing angle until they become parallel. The narrowest part of the track portion, where it is within percent of the narrowest width, extends a substantial distance D which is more than one-third the length of the track portion 286 of the merger accessory. This substantial distance D of the narrowed portion is desirable to stablize the vehicle so it is running straight along the track. Along almost all of the track portion, the height H of the walls is greater than the height V of the wheels, shown at 300 and 302, of a vehicle 304 which is designed to run along the merger accessory. Another connector 306 is located at the downpath end of the merger to connect to the track section 284.

Thus, the invention provides means with several accessories for novel operation and guiding of the vehicles and track sections therefor. Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modification and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is:

1. Apparatus for forming a looped toy vehicle path from flexible guide track sections comprising:

a pair of substantially identical base members, each having an upwardly curved vehicle guiding portion extending from a substantially horizontal end to an upwardly sloping end;

connecting means extending from each end for connecting a vehicle guiding track section thereto in alignment with said ends, respectively; and

means securing said base members together in sideby-side relation with said substantially horizontal ends extending in respectively opposite directions whereby opposite ends of a section of flexible trackway may be connected to said connecting means at said upwardly sloping ends to form a helical loop. 2. Apparatus for forming a looped toy vehicle path from flexible guide track sections comprising:

a pair of substantially identical base members, each having an upwardly curved vehicle guiding portion extending from a substantially horizontal end to an upwardly sloping end;

tongue means extending from each end for connecting a vehicle guiding track section thereto in alignment with said ends, respectively; and

interlocking protuberances and sockets on said base members securing said base members together in side-by-side relation with said substantially horizontal ends extending in respectively'opposite directions whereby opposite ends of a section of flexible trackway may be connected to said connecting means at said upwardly sloping ends to form a helical loop. 

1. Apparatus for forming a looped toy vehicle path from flexible guide track sections comprising: a pair of substantially identical base members, each having an upwardly curved vehicle guiding portion extending from a substantially horizontal end to an upwardly sloping end; connecting means extending from each end for connecting a vehicle guiding track section thereto in alignment with said ends, respectively; and means securing said base members together in side-by-side relation with said substantially horizontal ends extending in respectively opposite directions whereby opposite ends of a section of flexible trackway may be connected to said connecting means at said upwardly sloping ends to form a helical loop.
 2. Apparatus for forming a looped toy vehicle path from flexible guide track sections comprising: a pair of substantially ideNtical base members, each having an upwardly curved vehicle guiding portion extending from a substantially horizontal end to an upwardly sloping end; tongue means extending from each end for connecting a vehicle guiding track section thereto in alignment with said ends, respectively; and interlocking protuberances and sockets on said base members securing said base members together in side-by-side relation with said substantially horizontal ends extending in respectively opposite directions whereby opposite ends of a section of flexible trackway may be connected to said connecting means at said upwardly sloping ends to form a helical loop. 